Who're Gonna Call?
by Sugarrush71
Summary: A Castle Halloween Bash 2015 Entry. A very AU first meeting of Richard Castle and the best Ghostbusting team in the NYPD.


_A/N : Just taking a little break from my long ongoing story for this bit of fun. As I'm going to be somewhere that celebrates Halloween this Saturday I thought I'd contribute to the Castle Halloween Bash this year and so this idea came about. This could be conidered a crossover but I haven't marked it so. If people think it should be please let me know._

 _Disclaimer : Castle and Ghostbusters are not owned by me but by the creative minds that came up with them._

* * *

Richard Castle sits in the basement office of the 12th Precinct and looks around with barely contained enthusiasm. He is dragged from this eager cataloguing of all the items around the room by the middle aged, balding African American man with a neat moustache sitting behind the only desk in the room.

"Look, Mr Castle, are you sure you want to do this? For all the media hype this job isn't glamorous. It's dirty and difficult interspaced with times of extreme boredom between call outs. I'm sure you could find other units within the NYPD worth your time to follow for research, homicide maybe," the man in the black NYPD utility coveralls and Captain's bars on his collar suggests to him.

Castle grins charmingly at the man despite his tone indicating that he really wishes Castle hadn't called in a favour from his friend the Mayor to finagle to ride along with the man's unit.

"Captain Montgomery, I assure you that I won't get in your team's way if that's what you are worried about. To be frank I'm starting a new series of books in a new genre and I thought your unit would be the best place to get a truly authentic feel for this world. I've done my research and your team is the best in the city and I want…no, need to observe the best," argues Castle pleasantly.

"Well, be as that maybe but following around a PCU team is no picnic. There is real danger in what my people do so I don't like the idea of some untrained civilian getting in their way and putting themselves or my people at risk," counters Montgomery.

"Captain, I have signed all the necessary waivers that 1PP and the Mayor's office could come up with. If anything happens to me then I only have myself to blame and I promise neither I nor my family will hold you or your people responsible. I also promise not to interfere with your team's work. They won't even know I'm there half the time," he grins charmingly at the Captain again while at the same time having crossed the fingers on the hand that is resting on his knee and that the Captain can't see regarding the last part of that statement.

Montgomery contemplates Castle with scepticism but before any more arguments can come from the man he is interrupted by the ringing of the phone on his desk.

"Montgomery!" the man declares down the phone after picking up the handset.

As the Captain engages in a discussion with the person on the other end of the phone Castle sighs and returns to his study of the room. After all it's not every day that a bestselling novelist gets to sit in the office of the best Ghostbusters team in New York.

He can still remember back when he was a kid, living in that small two bedroom walk-up with his struggling actress of a mother, when the first 'outbreak' of paranormal activity happened in the city. It culminated with the giant Stay Pufft marshmallow man stomping its way down the streets of Manhattan. His mother had just barely been able to grab him and keep him from leaving the apartment that night so that he could go and see the phenomenon for himself. Instead he'd had to make do with watching the whole event unfold on TV.

Then a few years later after everything seemed to have died down the second 'outbreak' had occurred with that psycho-active slime coming up from the sewers. Fortunately on that occasion due to their fun filled household none of their infected appliances turned on his mother or himself. In fact, by the end of the night, his mother was leading a line-up of the toaster, electric kettle and vacuum cleaner in a conga line type dance around the apartment. At the time his budding writer's imagination had been enthralled with the opening up of the paranormal world but many years later, instead of inspiring him to write fantasy fiction, he went into murder mysteries.

It was after the second outbreak and with paranormal activity still prevalent in the five boroughs that the government decided that dealing with such occurrences shouldn't be left to well-meaning but under resourced amateurs. The powers that be decided that the four men that comprised the first private Ghostbusters team, while lauded for saving New York from disaster twice, were not enough to contain the reports of spectres, poltergeists, possession and other paranormal phenomena that were now part of daily life in the Big Apple.

So, after paying what the press rumoured were large yet undisclosed sums to the members of that original team for the rights to use their technology, New York City created their own Paranormal Containment Units, or PCUs, within the NYPD. Of course regardless of what bureaucratic acronym the teams were given everyone still called them Ghostbusters.

It is therefore after struggling with an extremely long bout of writer's block following his killing off of his character Derrick Storm that Castle has decided to take his writing into a new direction and try his hand at writing fantasy and the supernatural. To that end and after a lot of string pulling he now finds himself sitting in, what his research has told him, is the offices of the Ghostbusters team of the NYPD with the highest bag and tag rate in the city.

Castle is dragged from his thoughts by a knock on the Captain's office door and Montgomery, still on the phone, waves at someone over Castle's shoulder to enter the room. Castle turns in his seat to regard the newcomer and his heart skips a beat.

Walking into the office with a confident stride and with a curious look on her face is one of the most beautiful women Castle thinks he has ever seen. She is tall, almost tall as him and the stained and dirty black NYPD coveralls that she is wearing don't hide the strong yet very appealing figure of the woman's body. She has her auburn almost dark red hair cut short and her face is covered in black soot and a hint of green slime but the rest of her striking features are topped with piercing hazel eyes that have Castle forgetting how to form words for a moment.

Then his heart skips another beat as the woman's gaze, whose surname is Beckett he surmises from the patch he can see above one breast of her coveralls, turns on him. For the fraction of a second the woman's eyes widen and he thinks that perhaps she recognises him but just as quickly the woman schools her features and an unemotional and stoic visage takes prominence on her face. It is that quick alteration to her expression and the slightly wounded look in her eye that makes Castle think that the woman in front of him is trying to hide some pain behind the stiff attitude that she is trying to project. He wants to get to know this woman. To get to know the source of her pain and maybe help her. Plus he wouldn't say no to taking the beautiful woman out, showing her the town with them, hopefully, finishing at his bedroom in his loft.

Captain Montgomery then finishes his telephone call and addresses the newcomer to the room, "Ah, Beckett, there you are."

The woman, Beckett, makes a sidelong glance at Castle again before responding, "You wanted to see me, sir?"

'Yes, Beckett," says Montgomery who indicates with his hand towards Castle. "Let me introduce Richard Castle, the novelist. He's going to be following your team around for a while."

There is a sudden reddening of Beckett's cheeks and a rather indignant, "Sir?" bursts forth from her.

"Mr Castle here is looking to do research on the paranormal for a new book and has asked his friend the Mayor to be able to shadow a PCU team for research. He has chosen your team, Beckett."

"But..but…Sir! He can't…We can't…It's too dangerous and inappropriate. He'll get in the way and….," stammers Beckett desperately and if Castle didn't know better he would think that the woman wasn't honoured to have a ruggedly handsome author following her around.

Montgomery holds up his hand to stop Beckett's complaints, "Beckett, as much as I might agree with you, Mr Castle's presence here makes the Mayor happy and when the Mayor is happy the Commissioner is happy and when the Commissioner is happy I'm happy. You might as well make the best of it."

Beckett's mouth that was, to Castle, comically yet cutely hanging open at being interrupted snaps shut and she looks at him again with a now very angry glare. Time to work the Castle magic, he thinks.

"Officer Beckett….," he starts but is immediately interrupted by the woman.

"That's Sergeant Beckett to you, MISTER Castle," the grits through her teeth as with an eye roll she taps the chevrons on her sleeve that Castle admits he didn't see so captivated is he by the woman's looks.

"I apologise, Sergeant, I meant no offence and I promise you, just like I have Captain Montgomery, that I will not get in your way. I understand the importance of the work you and your team do for this city and my only goal is to observe you all as you perform that work with the efficiency and skill that I have heard about from so many sources," he ends giving her the most dazzling of his charming smiles. The same smile that has had him charm his way into many a woman's bed.

However, to Castle's dismay, all his words and smile seem to do is infuriate the woman as she gives a frustrated huff, crosses her arms across her chest and gives him another roll of her eyes.

"Sir, you can't be serious. He's supposed to come into the field with us?" Beckett tries again this time in an almost pleading tone towards her commanding officer.

"That's exactly what is going to happen, Beckett, and I expect you and your team to keep him safe," Montgomery then waggles a warning finger at her. "No, 'accidental' hits with a proton stream in the butt like happened to that building manager last week that tried to stop you pursuing that Class 3 onto his property."

Beckett ducks her head and Castle again wonders what it is about the woman that he even finds her frustrated, "Fine, Sir!" so adorable.

"So, Beckett, why don't you take Mr Castle here and introduce him to the rest of your team, show him the truck and start familiarising him with how we do things. Then he will accompany you on your next call. That is all, Sergeant," Montgomery dismisses the woman who then turns on the heels of her black combat boots and starts striding from the room.

Lost in the appealing sight of the rear of the woman as she walks away Castle forgets he is meant to follow her until she pauses, glares over her shoulder at him and in an annoyed tone asks, "You coming, Castle?"

* * *

Castle pulls his silver Mercedes to a stop behind the large PCU van, painted in the traditional NYPD blue and white livery, that has likewise come to a stop in front of the apartment building in Tribeca. As he turns off the engine he looks over with excitement and expectation at the woman seated in the passenger seat next to him. What he sees is a very annoyed Kate Beckett looking back at him.

It has been a few days since he turned up at the 12th precinct to start shadowing Beckett and her team. During that time he has been introduced to the rest of her unit, the tough, Latino, ex-special forces soldier Javier Esposito and the deceptively mild mannered and neatly dressed Irish man Kevin Ryan. He'd been given a full tour of the facility in the basement of the 12th where all their equipment was kept including the large, heavy duty containment unit. The unit where, after the experiences of those first Ghostbusters, their captures were temporarily held before being transported to the more permanent holding facility that has been built on Staten Island.

While there have been no call outs for Beckett's team yet he's used the time to attempt to bond with Esposito and Ryan, listen to their stories of their work and to ask as many questions about their closed off female superior as he can. For regardless or, he admits perhaps because, of how charmingly he acts towards her he can't seem to thaw her frozen heart towards him, or at the very least get her to crack a smile. He'd even bought the team a fancy new espresso machine after he tasted the monkey peed in battery acid concoction that passed for coffee in the team's break room as a means to ingratiate himself with them all and particularly Beckett. All she'd done at the sight of the shiny chrome machine was huff in annoyance and refuse to use it despite the pleasurable sounds Esposito and Ryan made after tasting the machine's creations.

Oh, there have been the odd moment of banter, almost flirting, between him and Beckett but she always cuts the interaction off before it can get going. It's almost as if she is afraid to let him, or anyone, to get too close. It makes him very puzzled because during their almost playful banter he perceives a bright and intelligent mind in Beckett that for some reason she is pouring into her work and not into the rest of her life.

This has been confirmed for him when he spoke to the other member of the 12th's PCU team, Dr Lanie Parish. It is a strange legal quirk that it was decided that despite the obvious evidence to the contrary every apparition, spectre or ghost that was captured by a PCU team had to be confirmed by a medical examiner that they were indeed dead before their essence could continue to be contained by the city. So it was Dr Parish's duty to inspect every capture, still in it's trap, before it was transferred to the larger containment unit here at the 12th and pronounce it so.

While the boys, as he had heard Beckett refer to Esposito and Ryan, hadn't really given him much personal detail regarding their team leader the sassy doctor and apparent best friend of Kate Beckett had been a bit more forthcoming. It was from the doctor that he learned that Beckett and her team had been detectives under Montgomery when they had encountered an apartment building where there was an old reservoir in the basement that held the last unknown and active amount of the psycho-reactive slime from over two decades previous. A murderer they were pursuing had discovered the reservoir and was using the slime to kill some of his neighbours in the building that he didn't like. Unfortunately for him the slime bonded onto his murderous intent, got loose, killed him and attempted to infest the building to murder the rest of the residents.

Beckett had led her team in successfully evacuating all the residents of the apartment building that were in danger from the frenzied psycho-altered appliances inside . That, despite not having any of the necessary equipment, they even managed to coral the threatening objects until the effects of the pink slime could be neutralised upon the arrival of a regular PCU team. Having been on the receiving end of it for the last couple of days he well believes Dr Parish's assertion that all it took was a glare from Beckett to cower the rampant machines in that building into submission.

After receiving commendations and medals from their superiors for their efforts Beckett's team had been encouraged to join the PCU under their current Captain. According to his medical informant it had taken some long and serious thought from Beckett and discussion between all three of them before they accepted the offer. Now here they are, the PCU team with the highest rate for successful captures in the whole NYPD.

Castle had despaired that he would ever see this team in action until this morning when Captain Montgomery had come out from his office and announced that they had 'a hot one'. As there are only three seats in the van that team use to transport their equipment to call outs he had to use his own car to follow the team to the scene. It had been Captain Montgomery that had ordered Beckett to accompany him in his car saying something along the lines that he wouldn't want them to loose him. The look that Beckett had given her Captain at that told him that it is what she was plainly hoping to do on the way to the scene. It also helped that he had another reason that he wanted to take his car to the scene and having a stunning yet serious Beckett with him was just an added bonus.

"OK, Castle, stay in the car," Beckett orders him sternly as she reaches for the door handle.

"Uh, Uh, Beckett. Captain Montgomery said that I can come with you everywhere you go so I'm going with you," replies Castle pleasantly but with a hint of determination.

The look that Beckett gives him at that would probably freeze a Class 5 slimer in it's tracks before she says, "Look, the Captain's not here and if you think I'm going to jeopardize the safety of a member of my team or even your self-entitled hide by bringing an untrained civilian inside with us you are crazy."

"But I swear I won't get in your way. I'll stay behind you and keep quiet, scouts honour," he pleads giving her his very best puppy dog eyes that not even his level headed teenage daughter, Alexis, can resist.

There is a long moment as Beckett regards him frostily before she rolls her eyes and throws her hands up in frustration, "Oh for Gods sake, OK. But if you get killed I will take extreme pleasure in trapping your ghostly ass myself."

"Ohhh, Beckett, you don't have to wait until I'm dead to get your hands on my ass. All you have to ask," he flirts with her while doing an internal fist bump at her saying yes to him going with her.

Rolling her eyes again and shaking her head she says, "Ugh, don't make me regret this already."

He just gives her his charming smile in response as she gets out of the car and hurries over to where Esposito and Ryan have opened up the back of their truck and have started strapping on their equipment. Castle follows her out of the car but not over to the truck.

Instead he makes his way to the trunk of his car that he released just before getting out, taking off his sport coat as he goes. It is there, at his open trunk, that Beckett later finds him zipping up his own black coveralls that have 'Castle' on a patch on one breast and 'Writer' on a patch on the other breast.

"What are you wearing?" she demands of him. Her eyes widen in shock when she sees what else he is reaching for from the trunk of his car. "And what the hell is that?"

"This, my dear Beckett," he replies as he hefts the object from the trunk and proceeds to shrug his arms into it's straps. "Is an original proton pack as used by the original Ghostbusters. Dr Venkman was having some cash flow issues after his reality show tanked so he sold me his original one for a song. Isn't it cool."

"But...but, how did you get fuel for it? Nuclear material doesn't exactly grow on trees," she asks him incredulously.

"Oh, I know a guy," Castle responds casually waving away her concerns.

Beckett eyes roam over the heavy machine on his back as he clips and tightens the straps of the pack securely to his body. Boy, is it heavy. He'd forgotten how heavy it is the few times he'd tried it out at the loft before Alexis banned it after he set the piano on fire after one unfortunate test firing.

He looks over at the much more streamlined, smaller and obviously lighter mat black pack that Beckett now has strapped to her back. After over three decades of R & D by some very interested defence contractors the version of the proton pack that Beckett and her team wear make the original one he is wearing look like the relic from last century that it is.

Castle sees a calculated look come across Beckett's face before she says innocently, shrugging her shoulders, "Oh, well. If you're sure you want to use that museum piece. It's just that if you are intent on coming with us I was going to let you use our spare pack. The report is there is a Class 3 screamer in there and they can be dangerous so I was going to let you go in armed but if you are dead set on using that..."

"Oh, no," interrupts Castle. "Please, I'd love to try one of the new packs that you use," he tells her enthusiastically.

"Ok, well come with me it's in the back of the bus," had with a toss of her head she indicates for him to follow her over to their truck.

Which Castle does as quickly as his legs will carry him as she leads the way over to the open door of the PCU truck. Smugly he registers the surprise on Ryan and Esposito's faces as they see how he is dressed and the pack on his back.

Beckett stops at the open door of the truck and indicates with her hand, "It's way in the front. Just climb in and you'll see it there. We'll wait here while you swap it out. Just hurry otherwise the ghost will be gone before we get in there."

Nodding in eagerness Castle clambers into the back of the truck and looks around the assorted equipment inside for the pack Beckett mentioned. Before he can ask where it is the light thrown from the open back door is gone and he is plunged into darkness as the door suddenly slams shut. He next hears the sound of the door being locked soon followed by receding laughter and he realises he's been duped.

He should have known that Beckett had given too easily to him following her inside. Castle turns on the LED torch light that he added to the strap of his pack and goes to the door to see if he can open it from the inside. While there is a handle it won't budge confirming that they really have locked him in. He then sweeps his light around the interior of the van looking for something to let him out. While normally he would love to inspect all the equipment he can see on hanging on one wall or in the metal baskets fixed to the other there isn't anything he can see that will release him from his prison.

Then there is a squawk from the remaining personal radio that he can see in a charger on a shelf at the front of the truck.

" _Ok, Beckett. I'm in the north stairwell heading up,"_ says the radio distorted voice of Esposito.

" _Copy that. I'm in the elevator heading to four. Ryan, have you got the trap set up yet?"_ comes the no nonsense tone of Beckett.

" _I'm at the bottom of the south stairwell now. I'll have the trap set in five,"_ says Ryan.

Damn, thinks Castle, I'm going to miss it. The boys had told him of their usual tactic in an apartment building like this. One of them would approach the floor with the ghost using one route while another would approach using an alternate route. They would then use short, controlled bursts from the proton packs to drive the ghost towards the only open escape route and right into the trap. A pretty standard take down and he wouldn't even get a chance to use his own pack to help.

Well, he's not totally helpless as he bends down to inspect the lock on the back door of the truck. He then unzips one of the pockets on the leg of his coveralls and pulls out the set of lock picking tools he has there. He had intended using them to try and impress Beckett in case they had to force their way into an apartment to find the ghost but at least he'll be able to show them that they can't lock him away from the action.

He's just about got the door unlocked when there are further calls from the radio behind him.

" _I'm at the exit of the stairwell onto four now. You in position, Beckett?"_ says Esposito.

" _Copy, I'm holding the elevator on four ready to go. Ryan, are you ready?"_ says Beckett.

" _Rodger, guys. Trap is set and I've taken cover position at the door leading to the garage so it can't escape that way,"_ says Ryan.

" _Ok, on my mark, Espo,"_ says Beckett. _"One...Two...Three, Go, Go. Go"_

Just as there is a satisfying click from the lock he is working on he hears a frantic call on the radio.

" _Target in sight...Oh, shit, it's a shredder!"_ comes the disconcerted voice of Esposito.

Castle pauses in the process of pushing open the now unlocked door to stop and listen with concern to the exchange on the radio. The PCU teams classify the different types of ghosts on a scale from one to five depending on how dangerous they are. Five for harmless and one for the most dangerous. The teams also give nicknames for the distinct types of ghosts within each class. The boys had given him a brief run down of some of the names they use so when he hears Esposito say the word shredder he stills with just a little fear.

Shredders are a Class 2 very ugly, very angry spirit. They look like a decaying corpse covered in a shredded cloak that flows around them as the float above the ground but it is not their clothing that gives them their name. No, shredders have long arms with long talons for fingers and even though they are spectral the force of the emotion from the ghost means that if slashed by their talons a person feels it and is hurt by it just as if it were the claws of a tiger.

There is silence from the radio for a moment and Castle goes to it to pluck it out of the charger. He fixes the radio to a purpose made slot on the other strap of his pack and then turns and steps out of the truck. As he pauses on the street behind the truck, looking up at the front of the building to the floor where Beckett's team is he hears more from the radio he's acquired.

" _Ok, I see it, Espo. It's in the corridor between you and me,"_ comes Beckett's voice. " _Change of plan. Go to full charge and hit it with a sustained burst. Drive it past me and then I'll step out and join you. We'll drive it together to to the end of the hallway and hold it there. Ryan, you get up the south stairwell fast and use the mobile trap to get it as we hold it. We can't risk this thing running loose."_

" _Copy, Beckett. On my way up now,"_ responds Ryan.

" _Firing now,"_ says Esposito.

There is silence for a while and so Castle walks over and enters the empty foyer of the evacuated building. Then he hears Beckett's straining voice come over the radio, " _Argh, Ryan! Are you there yet? This thing is strong. It's about to break free of our streams."_

" _I'm here. I'm just about to...,"_ says Ryan but then Castle hears a load crash that doesn't come from the radio but from the stairwell door over to his right.

" _Hell! It's loose,"_ says Beckett's angry voice.

" _You, think!"_ says the indignant voice of Ryan. " _It just blew past me. I ducked just in time otherwise it would have ripped my face off. It's heading down the stairs. I'm in pursuit."_

" _We're right behind you, bro,"_ comes the panting voice of Esposito.

Castle thinks that right about now might be a good time to arm his pack so he reaches behind his shoulder to release the stick. With it in his hand he flicks a switch he had added there and the pack behind him clunks and whirs into life. Then there is a sustained hum and his back starts to sweat as the machine on his shoulders starts generating significant heat. He twists the stick in his hands and the clear projection crystal extends from the end of the stick. Nervously he turns towards the door where the crash came from earlier hoping that the shredder decides to keep going down to the building's basement garage and not come out into the lobby. Suddenly following Beckett and her team doesn't seem that good an idea anymore.

His nervousness isn't helped by the next words from Ryan he hears from the radio, " _Wait...it's stopped on the ground floor...it's going back and forth as if it can't decide whether to keep going down or to exit there...it's..."_

But that Ryan was going to say that the ghost was exiting onto the lobby becomes very apparent to Castle as the frightening sight of the shredder appears in front of him. It passes through the door leading to the stairwell only leaving an outline of clear goo on the door to mark it's passing. The ghost immediately catches sight of Castle standing open mouthed in front of it. It lets out a fingernails on a blackboard cry and advances towards him.

Castle frantically points his stick at the terrifying form heading towards him and depresses the trigger. At that a blinding, flexing beam of red energy springs from the end of the stick and, more through luck than any practiced aim, impacts the ghost squarely in the chest.

There is a pained howl from the ghost as the red energy stream pushes it's form away from him. Castle struggles with the feedback from the stick as he tries to keep the stream centred on the ghost. Then, to his mind unfairly, the ghost seems to do a sidestep in mid air, dodges his beam and starts moving towards the front doors of the building and the outside world.

Still holding his finger down on the trigger he tracks the bucking stick in his hands to follow the ghost paying no heed of the damage he is causing to the lobby as his beam cuts a swathe across the walls and fixtures. Just before the ghost reaches the front doors he is able to centre his beam on it again. This time the red beam coils itself around the ghost and he feels his feet slip on the tiled floor beneath him as he is dragged forward with the continuing momentum of the ghost.

Arms quickly tiring from the exertion placed on them both in trying to keep the beam on the ghost and from the pull the spectre is effecting on him it is with relief that he registers the slamming open of the stairwell door behind him. There is a few seconds pause which if he wasn't so occupied he would take delight in the no doubt shocked faces of Beckett's team as they take in the sight of him doing their job for them.

Then he hears the commanding voice of Beckett, "Espo, go right and hit it low. I'll go left and hit it high. Ryan get ready with that trap. Umm...Castle, just keep holding it there. When Espo and I hit it watch that you don't get your stream mixed with ours."

Out of the corner of his eyes he see's Beckett and Esposito appear on either side of him and then two blue twisting beams of energy join his in ensnaring the shredder. He immediately notices a difference as the force from the ghost pulling him towards the doors stops and he takes a moment to look over at Beckett. Her newer design of pack obviously has some feedback dampeners in the gun shaped projector she is holding as she is holding hers steadily on the target. With her short hair blowing around her in the wind generated by the beams and her features lit from below from her blue stream he doesn't think he's seen anything more beautiful.

A sudden increase of the bucking of his own stick and a shower of sparks from the crystal at the end has Beckett look over at him and she shouts, "Focus on your stream, Castle. You almost crossed mine then."

Castle quickly turns his attention back to the stick in his hand and the stream of energy he is using to hold the ghost in place. He then feels a hand on his shoulder as Ryan steps up next to him. The man places a black disc on the floor at his feet that looks like one of those robotic vacuum cleaners. Then using the controller in his hand he manoeuvres the remote controlled trap into position under the screaming ghost.

In his ear he hears Ryan say, "On the count of three I'll activate the trap. Don't look at the light for more than a second otherwise it might damage your eyesight."

Beckett seeing the trap in place then shouts over the din coming from the restrained ghost, "On my mark, Ryan. One...Two...THREE!"

Ryan presses a button on his controller and a blinding cone of white light projects from the trap and envelopes the ghost. As they all look away from the bright light Beckett calls out, "Cease fire!"

Castle obeys and releases his finger from his trigger. The bucking of the stick stops and his arms drop to his sides in exhaustion. He looks at Ryan, who has donned protective goggles, as he is watching the progress of the ghost into the trap. A few seconds latter Ryan presses another button on his controller and the lobby returns to it's normal lighting levels as the trap closes. They all look back at the trap and Castle sees it sitting there, smoking slightly with a blue LED light on it's top flashing away.

"Clear!" calls Esposito.

"Clear!" calls Beckett.

"Clear and Contained!" calls Ryan after he has gone up to the trap and read the readout on the small LED screen on the top of it.

With a sigh of relief Castle looks around at the three members of the PCU team who all look back at him with different expressions on each of their faces. Ryan is looking at him with approval. Esposito is looking at him with incredulity. While Beckett is looking at him with an arched eyebrow and a look that is equal surprise and annoyance.

"That was so AWESOME!" exults Castle all feelings of fear at being confronted with a very dangerous ghost now gone from his mind.

"You might want to rain in the celebration in there a bit, hot shot, and get your cheque book out," says a teasing Beckett.

"Huh?" questions Castle.

Beckett points behind him and he looks around and then truly takes in the damage he caused to the lobby during his brief battle with the shredder. At the sight of the still smouldering walls and destroyed fixtures he calculates in his head how much the repairs are likely to cost. When he comes up with a number he swears in Chinese.

* * *

Caste is just putting his proton pack into the trunk of his car when Beckett appears at his elbow arms crossed across her chest. He looks up at her and smiles, "My first bag and tag."

"Your last bag and tag," she cautions him.

"Oh, I don't know. I think I handled myself pretty well in there," he counters confidently.

Beckett ducks her head for a moment before looking back up at him and then grudgingly says, "Yeah, ok, you might have done alright. And you did stop a dangerous Class 2 from escaping so for that I thank you."

"See, that wasn't so hard," teases Castle. He almost jumps for joy when a small smile appears on Beckett's face at his words. Has he managed to melt the ice queen's heart?

"But seriously, Castle. You pull a stunt like that again and I'll shove that piece of antiquated junk so far down your throat you'll have to bend over to shoot a ghost," counters Beckett.

"Does that mean that you'll let me keep shadowing you?" Castle asks hopefully having picked up on the loophole in Beckett's words.

Fixing him with a playful look she says, "Maybe. At the very least I can't let you roam the city with that thing without some adult supervision."

Happy and confident now that she it letting him stay he takes a step towards her and in his deep, bedroom voice he asks, "So, did you want to debrief me about today's events?"

Surprisingly for him she takes a matching step closer to him and says in husky voice, "Oh, I don't know, I don't think you can handle one of my debriefings."

Standing now as close to her as possible without actually touching he looks her in the eye and says, "I think I can handle it. I have a pretty good idea what to expect."

He is even more surprised as she leans her head forward and for a split second he thinks she is going to kiss him but at the last moment she moves her mouth to his ear and whispers with hot breath, "Oh, no, Castle. You have no idea."

As he stands there dumbfounded and aroused she pulls back, gives him a playful smile that ends with her biting her lower lip and she then turns around and saunters away from him. Her hips are definitely swaying as his lust addled brain watches her delectable rear move away from him.

It takes a moment for a coherent thought to register in Castle's brain again but when it does he thinks to himself that his future is looking like it is going to be one hell of an adventure.

* * *

 _A/N : There you have it. As I said just a bit of fun that is complete for now but who knows I may dabble in this universe again. I'm not 100% knowledgeable about Ghostbusters lore as it's been a while since I've watched the films but with the remake coming out soon this idea just came to me. I hope you enjoyed it._


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